.\" ****************************************************************************
.\"  RECORDER.3                                                recorder library
.\" ****************************************************************************
.\"
.\"   File Description:
.\"
.\"     Man page for the recorder library
.\"
.\"     This documents RECORDER, RECORDER_DEFINE and RECORDER_DECLARE
.\"
.\"
.\"
.\"
.\"
.\"
.\" ****************************************************************************
.\"  (C) 2019-2020 Christophe de Dinechin <christophe@dinechin.org>
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.TH RECORDER 3  "2019-03-09" "1.0" "Recorder Library"

.\" ----------------------------------------------------------------------------
.SH NAME
.\" ----------------------------------------------------------------------------
RECORDER, RECORDER_DEFINE, RECORDER_DECLARE \- Declare and define buffers to record events


.\" ----------------------------------------------------------------------------
.SH SYNOPSIS
.\" ----------------------------------------------------------------------------
.nf
.B #include <recorder/recorder.h>
.PP
.BI "#define RECORDER(" recname ", " recsize ", " rechelp ") ..."
.BI "#define RECORDER_DEFINE(" recname ", " recsize ", " rechelp ") ..."
.BI "#define RECORDER_DECLARE(" recname ") ..."
.fi
.PP


.\" ----------------------------------------------------------------------------
.SH DESCRIPTION
.\" ----------------------------------------------------------------------------
.PP
The
.BR RECORDER()
macro defines a buffer named
.I recname
to store up to
.I recsize
events for use by the
.BR record (3)
function. The
.I rechelp
string is self-documentation describing the events stored in the buffer.
This self-documentation can be displayed by activating the
.BR help
trace, see
.BR recorder_set_trace (3).

.PP
The
.BR RECORDER_DECLARE()
macro declares an event recorder, and can be used in header files.

.PP
The
.BR RECORDER_DEFINE()
macro is an alias for
.BR RECORDER(),
the intention being that you would use
.BR RECORDER()
for event recorders that are local to a file, or a
.BR RECORDER_DECLARE()
(in the header file) paired with
.BR RECORDER_DEFINE()
(in a non-header file) for event recorders that are shared across
multiple translation units.

.PP
These macros should be used at file scope, i.e. where a function
definition or global variable is allowed.

.PP
Each recorder is associated with a
.I trace value
which is an integer value that can be read using
.BR RECORDER_TRACE (3).
See
.BR recorder_trace_set (3).


.\" ----------------------------------------------------------------------------
.SH EXAMPLES
.\" ----------------------------------------------------------------------------
.PP
The program below records its input arguments, and crashes if passed
.I crash
as the first command-line argument.
.PP
.in +4n
.EX
#include <recorder/recorder.h>
#include <string.h>

RECORDER(program_args, 32, "Program command-line arguments");
int main(int argc, char **argv)
{
    int a;
    recorder_dump_on_common_signals(0, 0);
    for (a = 0; a < argc; a++)
        record(program_args, "Argument %d is %+s", a, argv[a]);

    if (argc >= 2 && strcmp(argv[1], "crash") == 0)
    {
        char *ptr = NULL;
        strcpy(ptr, argv[1]);
    }
}
.EE
.in -4n
.PP
When a crash occurs, previously recorded events are printed out on the
console.

.PP
The program below is an instrumented version of the classical
recursive Fibonacci computation. It uses several recorders
corresponding to different types of events, and activates warnings and
errors in a way that can be configured by setting an environment variable.
.PP
.in +4n
.EX
#include <recorder/recorder.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

RECORDER(fib_main,    32, "Loops in fib function");
RECORDER(fib_loops,   32, "Loops in fib function");
RECORDER(fib_warning, 32, "Warnings in fib function");
RECORDER(fib_error,   32, "Errors in fib function");

int fib(int n)
{
    if (n <= 1) {
        if (n < 0)
            record(fib_error, "fib is undefined for negative value %d", n);
        return n;
    }
    record(fib_loops, "Computing fib(%d)", n);
    int result = fib(n-1) + fib(n-2);
    record(fib_loops, "Computed fib(%d) = %d", n, result);
    return result;
}

int main(int argc, char **argv)
{
    int a;
    recorder_dump_on_common_signals(0, 0);
    recorder_trace_set(".*_warning=35 .*_error");
    recorder_trace_set(getenv("FIB_TRACES"));
    for (a = 1; a < argc; a++) {
        int n = atoi(argv[a]);
        if (n >= RECORDER_TRACE(fib_warning))
            record(fib_warning, "Computing for %d may take a while", n);
        printf("fib(%d) = %d\n", n, fib(n));
        if (n >= RECORDER_TRACE(fib_warning))
            record(fib_warning, "Computation for %d finally completed", n);
    }
}
.EE
.in -4n
.PP
This program will produce an output similar to the following:
.PP
.in +4n
.EX
% fib 1 2 3 4 10 20 30 35 10 40 -1
fib(1) = 1
fib(2) = 1
fib(3) = 2
fib(4) = 3
fib(10) = 55
fib(20) = 6765
fib(30) = 832040
[2714667 0.177725] fib_warning: Computing for 35 may take a while
fib(35) = 9227465
[32575370 1.859156] fib_warning: Computation for 35 finally completed
fib(10) = 55
[32575547 1.859171] fib_warning: Computing for 40 may take a while
fib(40) = 102334155
[363735828 20.527882] fib_warning: Computation for 40 finally completed
[363735829 20.527887] fib_error: fib is undefined for negative value -1
fib(-1) = -1
.EE
.in -4n
The first column in trace outputs is the number of events that were
recorded. THe second column is the time in seconds since the program
started.

.PP
The same program can also be run with additional tracing or warnings,
for example:
.PP
.in +4n
.EX
% FIB_TRACES="recorder_location fib_loops fib_warning=3" /tmp/fib 3 4
/tmp/fib.c:33:[82 0.000496] fib_warning: Computing for 3 may take a while
/tmp/fib.c:18:[83 0.000561] fib_loops: Computing fib(3)
/tmp/fib.c:18:[84 0.000570] fib_loops: Computing fib(2)
/tmp/fib.c:20:[85 0.000575] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[86 0.000581] fib_loops: Computed fib(3) = 2
fib(3) = 2
/tmp/fib.c:36:[87 0.000590] fib_warning: Computation for 3 finally completed
/tmp/fib.c:33:[88 0.000596] fib_warning: Computing for 4 may take a while
/tmp/fib.c:18:[89 0.000601] fib_loops: Computing fib(4)
/tmp/fib.c:18:[90 0.000607] fib_loops: Computing fib(3)
/tmp/fib.c:18:[91 0.000612] fib_loops: Computing fib(2)
/tmp/fib.c:20:[92 0.000619] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[93 0.000625] fib_loops: Computed fib(3) = 2
/tmp/fib.c:18:[94 0.000664] fib_loops: Computing fib(2)
/tmp/fib.c:20:[95 0.000707] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[96 0.000724] fib_loops: Computed fib(4) = 3
fib(4) = 3
/tmp/fib.c:36:[97 0.000741] fib_warning: Computation for 4 finally completed
.EE
.in -4n


.\" ----------------------------------------------------------------------------
.SH BUGS
.\" ----------------------------------------------------------------------------
.PP
Incorrect use of the macros generally results in nonsensical compiler diagnostics.

.PP
Bugs should be reported using https://github.com/c3d/recorder/issues.


.\" ----------------------------------------------------------------------------
.SH SEE ALSO
.\" ----------------------------------------------------------------------------
.BR record (3),
.BR record_fast (3)
.br
.BR recorder_trace_set (3)
.BR RECORDER_TRACE (3)
.br
.BR recorder_dump (3),
.BR recorder_dump_for (3),
.br
.BR recorder_configure_output (3),
.BR recorder_configure_show (3)
.br
.BR recorder_configure_format (3),
.BR recorder_configure_type (3)

.PP
Additional documentation and tutorials can be found
at https://github.com/c3d/recorder.


.\" ----------------------------------------------------------------------------
.SH AUTHOR
.\" ----------------------------------------------------------------------------
Written by Christophe de Dinechin
